Prediction of an intradialytic morbid event (IME) during hemodialysis (HD) is difficult in clinical practice because no reliable and accurate technique is available. An IME is typically defined by a patient's systolic blood pressure (SBP) decreasing to less than about 90 mmHg and a heart rate (HR) greater than about 100 beats/min with muscle cramps, dizziness or fainting of the patient, often leading to the need to discontinue ultrafiltration before the end of an HD treatment. Monitoring of relative blood volume (RBV) by means of a device such as CRIT-LINE™ (Hema Metrics, Kaysville, Utah, see U.S. Pat. No. 5,803,908) or blood volume monitor (BVM, Fresenius AG, Germany) has been used to assess critical thresholds of RBV which may indicate the risk of an IME. See C. Barth, W. Boer, D. Garzoni, T. Kuenzi, W. Ries, R. Schaefer, D. Schneditz, T. Tsobanelis, F. van der Sande, R. Wojke, H. Schilling, and J. Passlick-Deetjen, “Characteristics of hypotension-prone haemodialysis patients: is there a critical relative blood volume?,” Nephrol Dial Transplant, vol. 18, pp. 1353-60, July 2003. However, the relationship between a change in RBV and an IME depends on multiple factors including, but not limited to, ultrafiltration rate (UFR), degree of fluid overload, plasma refilling rate, and autonomic nervous system control. For this reason, measurement of changes in RBV alone fails to reliably predict an IME. See D. N. Reddan, L. A. Szczech, V. Hasselblad, E. G. Lowrie, R. M. Lindsay, J. Himmelfarb, R. D. Toto, J. Stivelman, J. F. Winchester, L. A. Zillman, R. M. Califf, and W. F. Owen, Jr., “Intradialytic blood volume monitoring in ambulatory hemodialysis patients: a randomized trial,” J Am Soc Nephrol, vol. 16, pp. 2162-9, July 2005.
Therefore, there is a need for a more reliable method of predicting the occurrence of an IME in a patient having excess fluid removed by ultrafiltration during a hemodialysis treatment.